2020 Fiscal Year Final Research Report
Development of local surface alloying method using tool wear during friction stir processing
| Project/Area Number |
19K23575
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Multi-year Fund |
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| Review Section |
0401:Materials engineering, chemical engineering, and related fields
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| Research Institution | Osaka University |
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Principal Investigator |
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| Project Period (FY) |
2019-08-30 – 2021-03-31
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| Keywords | 摩擦攪拌プロセス / ツール摩耗 / 表面合金化 / 炭化タングステン / 鉄鋼材料 / 固溶 / 界面反応 / メカニカルアロイング |
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| Outline of Final Research Achievements |
Friction stir processing (FSP) is an effective surface modification technique to refine and homogenize microstructures in a solid state for various metallic materials. However, the tool wear has been considered as the unavoidable issue in FSP of high strength materials. In this study, the effects of tool constituent elements added to several steels due to WC tool wear during FSP on the microstructural evolution were investigated, and a new alloying process was developed based on the phenomenon. In addition, in order to clarify the alloying mechanism, a tool/steel interface frozen during FSP was observed. It was found that the compound layer was generated by the reaction of WC particles and Fe atoms on the steel side and decomposed under high temperature and high pressure, followed by the W and C dissolution into the steel matrix.
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| Free Research Field |
溶接・接合工学
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| Academic Significance and Societal Importance of the Research Achievements |
多くの研究者が“摩耗しないツール”の開発に注力するばかりで，摩耗したツール材と鉄鋼材料との間で生じる組織変化に着目した研究自体がほとんどなく，本研究はFSP中に生じるツール側の組織変化から鋼側への元素移動までを材料科学的に詳細に捉えた最初の研究となった．また，本現象を逆活用することにより，鋼構造物中の所望の領域に対してのみ，高疲労強度や高耐摩耗性を付与することが期待でき，ひいては製品設計上の材料選択における自由度の大幅な拡大が実現可能であると考えられる．
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